“Who is the liar?” asks the writer of 1 John.
The liar is the one who denies that Jesus is God.
Who is the father of liars, of lies? Our great adversary who gave up his place in heaven to rule in hell, per Milton in PARADISE LOST is the father of lies, of liars. Satan tells the great lie to Eve and Adam, promising them they can be as gods if they disobey God. The cost of believing this lie is immeasurable.
People are deceived. People do prefer to live in darkness so the light does not show their deeds — which are deeds of the darkness, and not of the light. (John 3: 19 – 20)
Satan likes keeping people in the darkness, lest they see the light and prefer it. Hence, Satan lies about everything, keeping people in confusion as they try to figure out what is the truth. Satan’s favorite lie is the one of the anti-Christ — the one which tells the world that Jesus is a good teacher, but not the Son of God, not the expected Messiah of Israel, not the only way to paradise — that is, eternal life in the very presence of God the Father, God the Son, God the Holy Spirit.
Jesus is a good teacher, says Satan. Pay attention to him, follow his rules, believe his little parables, but do not commit your self to him, do not believe he saves you. For this belief is foolishness. Satan lies.